The present invention relates to an optical recording and reproducing apparatus for optically recording and reproducing information on and from a disk-shaped information carrier having a guide track, and more particularly to an optical recording and reproducing apparatus which controls an intensity of a recording light beam of a laser light source by an address signal of the guide track.
An optical information recording and reproducing apparatus has been proposed, in which a disk-shaped information carrier having photo-sensitive material applied or vapor-deposited thereon is rotated, a light beam from a laser light source which is converged to a small spot of a diameter of approximately 1 .mu.m is irradiated to the disk-shaped information carrier, an intensity of a light output therefrom is modulated with a recording signal to record information such as a video signal or a digital signal on the information carrier in real time as a change of an optical characteristic such as change of phase due to unevenness, change of index of refraction, change of reflection factor or change of transmission factor, and the recorded information is reproduced by detecting the change of the optical characteristic.
In such an apparatus, in order to allow a high density of recording tracks and partial writing or erasing of discrete tracks, it has been proposed to provide cocentric guide tracks or a spiral guide track for guiding the recording tracks, and the information is recorded or reproduced on or from a selected track while tracking control is effected so that the recording track follows the guide track.
The disk-shaped information carrier can store the information in a form which permits optical recording and reproducing and has the guide track to guide the information to the recording surface. The information is recorded and reproduced by optically tracking the guide track and producing an electrical signal which causes a small writing spot light to follow and focus to the guide track. The guide track has a phase structure which presents a phase change to the small spot light impinged to the information carrier. A disk having a guide track of phase structure is disclosed in IEEE Spectrum, Vol. 16, No. 8, p. 26, in which the guide track has a groove depth of one eighth of a wavelength, a low melting point metal such as Te is vapor-deposited on the groove, and address information is recorded in the same groove at a depth of one quarter of the wavelength. The information is written on the disk by forming holes by evaporating the low melting point metal by thermal energy of the small spot light.